Keywords

Abstract

A ﬂashover phenomenon is achieved through two successive phases:
the initiation of a discharge at the surface of the wet insulator
and the elongation of the discharge for ﬂashover, if the conditions
are favourable. On the other hand, if the partial arcs succeed in
covering a critical part of the leakage path, ﬂashover is practically
ensured. In the mathematical models developed for calculating the
critical ﬂashover voltage, the critical arc length has been determined
using the expression L/(n + 1) or having been used two-thirds of the
leakage length (L). In the proposed work, the authors’ intentions
were to eliminate the use of diﬀerent critical values of arc length
which were model speciﬁc and tried to ﬁnd the critical arc length
which should not be model speciﬁc but holds good for the modelling
of existing and well-accepted proﬁle of the porcelain disc insulators.
In this context, experiments were carried out on ﬁve porcelain disc
insulators at diﬀerent arc lengths to study the role of the underside
and top surface on ﬂashover voltage at diﬀerent pollution levels. The
analysis of the results obtained by elaborative ﬂashover experiments
conducted on the ﬁve insulators shows that the leakage distance
between the pin and the last rib (or the edge of the underside) is
the critical distance for ﬂashover to occur.